In today's oil and gas industry, wells that are deviated are most common and, more often than not, are deviated to horizontal. A horizontal well is typically straight and relatively flat over the final portion that extends between the heel and the toe. The shape prior to the heel will be whatever is necessary to get from the surface location to that heel, building to an inclination of roughly 90 degrees and turning to the intended azimuth, achieving both by the time the heel is reached. The heel and the toe may be referred to as endpoints and the portion between the heel and toe may be referred to as a lateral.
There are a number of established plays that utilize mass planning and targeting for horizontal drilling like the SAGD (steam assisted gravity drainage) in Canada and the Marcellus, Hornriver and Barnett shale gas plays. In order to optimize the number of wells to completely exploit one of these plays, companies are planning hundreds, and in some case thousands, of wells for an entire field, which is often very time-consuming and requires numerous resources. A field development plan therefore, will typically attempt to fill one or more predetermined polygonal areas with horizontal wells. An example of such a polygonal area is the area within a lease boundary, which has been reduced by a ‘setback’ distance (the minimum distance that all wells must be from the lease boundary). Each segment between any two sequential edge points along the boundary is thus, referred to as a boundary segment.
There are numerous types of resource plays that require laterals to be positioned and spaced to fill a lease boundary. Two specific plays that utilize the placement of laterals are shale and heavy oil plays. The objective is to maximize the production coverage within the lease boundary based on lateral constraints, such as min/max lateral lengths, lateral spacing and heel, toe, heel,heel or toe,toe spacing. In order to fully maximize the production coverage, the horizontal wells are laterally spaced in proportion while maintaining extremely accurate subsurface depth. Likewise, the available surface locations and surface/subsurface hazards must be taken into account when positioning the horizontal wells.
In order to address the foregoing concerns, conventional techniques, like that described in WIPO Patent Application Publication No. WO 2011/115600, have applied horizontal targeting to fill a predetermined area, within a regular or irregular boundary, with horizontal wells. The horizontal targeting initially considers the boundary filling as a two-dimensional (2D) problem. In FIG. 3, a plan view 300 illustrates a predetermined area within an irregular boundary filled by horizontal wells using a conventional technique. As demonstrated by the open areas 302, conventional techniques may not maximize the production coverage of the predetermined area by the horizontal wells because the predetermined area lies within an irregular boundary, the horizontal wells must always be parallel and/or the laterals must all have the same length.